Bonding apparatus are used in semiconductor assembly and packaging. An example of a bonding apparatus is a wire bonder, which makes electrical wire connections between electrical contact pads of semiconductor dice and a substrate—a process which is known as wire bonding. Specifically, a bonding wire is fed from a wire spool to a bonding tool (e.g. a capillary) to make the electrical wire connections between the semiconductor dice and the substrate during wire bonding.
One method of wire bonding uses a ball bond and involves a series of steps, as follows: i) melting a bonding wire tail that protrudes from a base of the capillary to produce a free air ball; ii) lowering the free air ball to an electrical contact pad of a semiconductor die; and iii) welding the free air ball to the substrate via ball bonding. The capillary then draws out a loop of the bonding wire starting from the ball bond and ending with a wedge bond to electrically connect the semiconductor die with the substrate. Thereafter, the capillary is raised to expose a length of bonding wire from the capillary base, before the bonding wire is clamped and pulled in a direction away from the substrate to detach from the wedge bond. This thereby forms another wire tail. The tip of the wire tail is then positioned at a fire level, where an Electrical Flame-Off (“EFO”) system applies a high voltage from an electrical torch to the wire tail to thereby melt the wire tail and produce a new free air ball that is used for a next ball bonding process with the semiconductor die.
The free air ball size is controlled by the EFO system current and exposure time, and is conventionally checked by a user who measures the size of the free air ball under a scanning electron microscope (“SEM”). If the FAB size does not meet the desired specification(s), the user would then need to adjust the EFO system current and/or exposure time manually. Thus, the productivity of the wire bonder is affected by such manual intervention to measure the free air ball size.
Accordingly, it is an object of this invention to ameliorate the above limitation of conventional wire bonder and to provide the general public with one or more useful methods to increase the productivity of wire bonders.